Re: light weight user level semaphores

[Linus Torvalds]

On Thu, 19 Apr 2001, Alexander Viro wrote:
>
> I certainly agree that introducing ioctl() in _any_ API is a shootable
> offense. However, I wonder whether we really need any kernel changes
> at all.

I'd certainly be interested in seeing the pipe-based approach. Especially
if you make the pipe allocation lazy. That isn'tr trivial (it needs to be
done right with both up_failed() and down_failed() trying to allocate the
pipe on contention and using an atomic cmpxchg-style setting if none
existed before). It has the BIG advantage of working on old kernels, so
that you don't need to have backwards compatibility cruft in the
libraries.

		Linus